This is my second flight flying with a private member at the airfield I work at.

The aircraft I flew in was the Yakovlev YAK 12M. I was in the backseat whilst two well-experienced pilots flew the plane. We intended to do a few circuits – so it was a relatively short flight!

Interestingly enough the pilot told me this particular YAK was used as an air ambulance. It was used by the Soviet Union to carry injured soldiers in stretchers. It would make sense given how vast in length the plane is.

Great experience!

I found a fact file sheet about the YAK in the cockpit. So here’s some information about the YAK:

First, the co-pilot and I did an exterior inspection and walk-around. We were looking for anything that could indicate the plane is not air-worthy. For example, possible fuel leaks, damaged control surfaces or missing rivets. This is few of what we’re looking for when doing a walk-around. As a pilot you want to be 110% sure the pilot is airworthy before taxiing the aircraft.

Here is the typical checklist for the YAK 12M:

• Look around the tyres and kick to feel the pressure
• Oil level at more than 8 litres
• Fuel levels: OK

Once we were satisfied with the exterior checks – the pilot carefully added aircraft oil into an inlet. He then turned the propeller 9 times to prevent hydraulic lock.

• The Yak has a radial engine.
• Hydraulic lock is possible in a radial engine.

What is a hydraulic lock in a radial engine?

• Radial engines have cylinders which ‘radiate’ outwards from the central crankcase.
• Radial engines are efficient – as they have a shorter crankshaft and fewer bearings – so they run smoother.
• Aircrafts with radial engines, like the Yak can suffer from hydraulic lock.
• Hydraulic lock occurs when the engine is cooled down and the oil seeps from the crankcase past the piston rings and collects in the lower cylinders (gravity it is called…). If there is enough oil collected this can result in hydraulic lock.
• Oil is incompressible – so to have it collect in the compression chamber is never a good idea. It will NOT compress. And when the piston reaches the top dead centre of the compression with the oil trapped – either the compression chamber will blow or the connecting rod will snap.
• So in summary, hydraulic lock is the phenomenon of enough oil collecting in the lower cylinders of a radial engine which can led to damage.

• To prevent this – the ground crew or pilot of the radial engine aircraft will turn the propeller a certain number of times BEFORE starting the plane. If extra force is needed to turn – then the chamber is in hydraulic lock in which a spark plug is removed and the oil is drained out. Otherwise you’re in for an expensive bill when you start the engine and the chamber or rod blows out during compression!
• Also, by the turning the propeller a few times the oil will leave the chamber – pass the piston rings and collect BACK into the crankcase.

Remove Before Flight Tags

And of course, we couldn’t forget the ‘Remove before flight’ protective covers over the pitot tubes. This is a protective, safety cover which is used on pitot tubes. Pitot tube is an air intake tube that is used to measure the airspeed of an aircraft. The covers are used primarily to prevent dust accumulating or small inspects crawling inside and blocking it. It’s important to remove these covers during the walk-around. This is something so small and yet so important. There are countless incidents where pilots have left these covers which could’ve and probably have led to major aircraft accidents.

Once we were in and strapped up the pilot completed a start-up and pre-flight checklist.

Here is the start-up checks we did:

• Switches off, magnetos off
• Fuel: OK
• Air on
• Brakes on
• Fuel on
• Mixture rich
• Close oil cooler
• Close carbs heat
• Open gills
• Flaps up
• For cold start: 9 blades, 1 prime each
• For warm start: 1 prime per 10 degrees below 100 cylinder head temp.
• Master switch on
• Generator on
• DC converter
• Starter on
• Set throttle
• Press starter when engine turns the correct way, mags on both
• When engine fires – set throttle and prime.
• Set 1000 rpm
• Close gills until cylinder head temp rises then open
• Open oil cooler (as necessary).

 We taxied to the runway and turned into the wind just short of the runway – here we completed a pre take-off checklist.

Here was our pre take-off checklist:

• Mags on both
• Trim set
• Flap to 15 degrees
• Fuel on and sufficient
• Mixture: fully rich
• Starter covered
• Primer locked
• Prop fully fine
• Oil temp green
• Cylinder head temp green
• Set DI to compass
• Switches on
• Controls full and free
• Hatches and harnesses secure

Our take-off checklist:

• Full power set (then back to 7.5 boost)
• Set prop to 2000 rpm
• Take-off with tail up or 3 point

Shortly after the plane sped up to 35 knots and we took off.

Here are the speeds for throughout the flight:

We completed 3 circuits around the airfield – including a planned missed approach. We landed and the pilot in command and I flew up again – this time with me in the front seat. I also took control of the aircraft as we flew out the airfield and completed a circuit up until the descent.

Here was our descent checklist:

• Reduce throttle
• Flaps extend below 140kmh
• Final approach 110kmh
• Set prop to fine
• The stick should be set back to ensure tail wheel locked – risk of ground loops.

Overall, it was a great experience and I really enjoyed it. It was great flying in a tailplane aircraft – you definitely require some sort of skill to take-off and land in a tailplane. It would be great to start flying more often in order to build my skills around being in command and navigating an aircraft.